According to CVE-2012-0056, linux kernel 2.6.39 and later versions is vulnerable to local privilege escalation by any local users due to the mem_write function does not properly check for permissions when writing to /proc/<pid>/mem, when ASLR is disabled.
Please take a look at this demonstration to see how it works.
Reference:
1. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2012-0056
2. http://blog.zx2c4.com/749
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Continue reading Linux local privilege escalation via SUID